1. Field of the Invention
Present invention relates to well devices employed in the completion and production of oil and gas wells. More specifically, the present invention relates to a well packer which is retrievably anchored in a subsurface location within a well casing or other well conduit.
2. Description of the Prior Art
Well packers are used to maintain sealing integrity between inner and outer concentric conduits within a well bore. When the packer is "set" or anchored in a subsurface location, gripping members or "slips" and annular resilient packing elements are extended radially to respectively anchor the packer to the casing and to form a pressure-tight seal between the packer body and the surrounding well conduit or casing. A production tubing string connected to the packer conducts well fluids which enter the casing below the packer to the well surface. A variety of well known techniques are employed to set the packer at the desired subsurface location. Manipulation of the tubing string or the application of fluid pressure through the tubing string are examples of two common techniques.
Retrieval of the set packer requires that the radially extended seals and slips be retracted from engagement with the surrounding conduit. Certain of the prior art packers were released from the set position by manipulating the tubing string to cause mechanical components in the packer to sever or shift to a position which permits the slips and seals to retract. Once released, the tubing string and attached packer could be withdrawn from the casing and retrieved to the well surface.
A straight pull release is preferred by many operators. Thus, many prior art packer designs are released by a straight upward pull of the tubing string. Such packers typically employ shear pins or other frangible devices which rupture when a sufficient shearing force is imparted through the tubing string. The shear pins must remain intact while the packer is set in its normal operating position but must be capable of rupturing when a predetermined retrieving force is exerted on the tubing string.
The present invention has as its object the provision of a well packer which is set by the application of fluid pressure through the tubing string and which is released by a straight upward pull on the tubing string.
Another object of the present invention is the provision of a straight pull release mechanism which provides a simple and effective method for varying the shearing force necessary to release the packer.
Another object of the invention is the provision of a straight pull release mechanism which is internal to the packer but which can be easily adjusted to vary the shear value of the release mechanism.